World Leaders Mark World War I Centenary; See Pictures

French President Emmanuel Macron and his wife Brigitte Macron welcome Turkey's President Tayyip Erdogan with his wife Emine Erdogan at the Elysee Palace as part of the commemoration ceremony for Armistice Day, 100 years after the end of the First World War, in Paris, France. (Image: Reuters)

US President Donald Trump takes part in the commemoration ceremony for Armistice Day, 100 years after the end of World War One, at the Suresnes American Cemetery and Memorial in Paris, France. (Image: Reuters)

French President Emmanuel Macron delivers his speech as he attends a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe in Paris, France. (Image: Reuters)

Russia's President Vladimir Putin leaves after a lunch at the Elysee Palace in Paris as part of the commemoration ceremony for Armistice Day, 100 years after the end of the First World War, France. (Image: Reuters)

Russian President Vladimir Putin shakes hands with US President Donald Trump as he arrives to attend a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe, in Paris, France. (Image: Reuters)

Russian President Vladimir Putin and Canadian Prime Minister Justin Trudeau attend the opening session of the Paris Peace Forum as part of the commemoration ceremony for Armistice Day, 100 years after the end of the First World War, in Paris, France. (Image: Reuters)

French President Emmanuel Macron and his wife Brigitte Macron and Canadian Prime Minister Justin Trudeau arrive at a commemoration ceremony for Armistice Day, 100 years after the end of World War One, at the Arc de Triomphe, in Paris. (Image: Reuters)

US President Donald Trump shakes hands with French President Emmanuel Macron as he arrives at a commemoration ceremony for Armistice Day, 100 years after the end of World War One, at the Arc de Triomphe, in Paris, France. (Image: Reuters)

French first lady Brigitte Macron poses with US first lady Melania Trump during a visit at the Chateau de Versailles (Versailles Palace) in Versailles, near Paris, as part of the commemoration ceremony for Armistice Day, 100 years after the end of World War One, France. (Image: Reuters)

French President Emmanuel Macron and his wife Brigitte Macron accompany US President Donald Trump and first lady Melania Trump after a meeting at the Elysee Palace on the eve of the commemoration ceremony for Armistice Day, 100 years after the end of the First World War, in Paris, France. (Image: Reuters)

Russian President Vladimir Putin talks with United Nations Secretary-General Antonio Guterres during a lunch at the Elysee Palace, as part of the commemoration ceremony for Armistice Day, 100 years after the end of the World War One at the Arc de Triomphe, in Paris, France. (Image: Reuters)

US President Donald Trump and German Chancellor Angela Merkel attend a commemoration ceremony for Armistice Day, 100 years after the end of the First World War, at the Arc de Triomphe, in Paris, France. (Image: Reuters)

French President Emmanuel Macron and German Chancellor Angela Merkel hug after unveiling a plaque in the Clairiere of Rethondes during a commemoration ceremony for Armistice Day, 100 years after the end of the First World War, in Compiegne, France. (Image: Reuters)

US President Donald Trump delivers a speech during a visit at the Suresnes American Cemetery as part of the Paris commemoration ceremony for Armistice Day, 100 years after the end of the First World War, France. (Image: Reuters)

German Chancellor Angela Merkel, US President Donald Trump, first lady Melania Trump, Morocco's King Mohammed VI and his son Crown Prince Moulay attend a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe in Paris, France. (Image: Reuters)

US President Donald Trump arrives to take part in the commemoration ceremony for Armistice Day, 100 years after the end of World War One, at the Suresnes American Cemetery and Memorial in Paris, France. (Image: Reuters)

French President Emmanuel Macron welcomes Luxembourg's Prime Minister Xavier Bettel at the Elysee Palace as part of the commemoration ceremony for Armistice Day, 100 years after the end of World War One, in Paris, France. (Image: Reuters)

US President Donald Trump, First Lady Melania Trump, and German Chancellor Angela Merkel attend a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe, in Paris, France. (Image: Reuters)

French President Emmanuel Macron pays his respects by the Tomb of the Unknown Soldier during a commemoration ceremony for Armistice Day, 100 years after the end of the First World War, at the Arc de Triomphe, in Paris, France. (Image: Reuters)

French President Emmanuel Macron shakes hands with US President Donald Trump during a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe in Paris, France. (Image: Reuters)

Russian President Vladimir Putin arrives to take his place with French President Emmanuel Macron, German Chancellor Angela Merkel, US President Donald Trump and first lady Melania Trump to attend a commemoration ceremony for Armistice Day, 100 years after the end of the First World War at the Arc de Triomphe in Paris, France. (Image: Reuters)

French President Emmanuel Macron delivers a speech during a commemoration ceremony for Armistice Day, 100 years after the end of the First World War, at the Arc de Triomphe, in Paris, France. (Image: Reuters)

US President Donald Trump and William M. Matz Jr, secretary of the American Battle Monuments Commission, attend a ceremony during a visit at the Suresnes American Cemetery as part of the Paris commemoration ceremony for Armistice Day, 100 years after the end of the First World War, France. (Image: Reuters)